1. Field of the Invention
The present invention relates generally to a bead support system having relatively movable parts that cooperate to define a bead-receiving groove, with the movable parts including a flexible sheath of material forming a cover that overlies a relatively rigid support, and with the cover having central portions thereof that are movable from side to side through the region of the groove so that a point-to-point non-slip type of engagement can be maintained between the cover and such bead portions as extend into the groove, whereby the bead portions are permitted to "rotate" through a limited range of movement while being retained in the groove without becoming malformed or distorted. More particularly, the present invention relates to the aforedescribed type of bead retention and support mechanism, and to methods of use thereof, wherein the relatively movable cover and support have interfitting, spline formations that extend transversely relative to the length of the groove 1) for drivingly interconnecting the cover and the underlying support so that forces can be transferred therebetween in directions that extend along the length of the groove, 2) for preventing relative movement of the cover and the support in directions that extend along the length of the groove, and 3) for permitting smooth-sliding side-to-side movements of the cover to occur in unison with bead "rotation" within the groove, whereby the cover maintains a point-to-point slip-free type of non distorting engagement with such bead portions as extend into the groove even during "rotation" of the bead portions within the confines of the groove.
2. Prior Art
Pneumatic tires typically are not manufactured by casting them in molds. Rather, they typically are assembled or "built" one at a time to form uncured or "green" tires that are put through a vulcanizing process to cure the rubber compound by causing cross-linking to take place under heat and pressure.
During the assembling or "building" of a green tire, components are assembled sequentially about a substantially cylindrical "tire building drum." During much of the tire building process, the tire building drum is rotated about a substantially horizontal axis that extends centrally, longitudinally through the tire building drum. The tire building drum and the equipment that supports and rotates the drum comprise major elements of what is referred to as a "tire building machine."
At the workstation of a tire building machine, the building of a tire typically begins with the application of an innerliner layer of rubber compound so that it extends in a continuous band about central portions of the tire building drum. Plys are added one at a time with the cords of each successive ply being carefully oriented in accordance with a predetermined plan. Beads are set in place, and the plys are "turned up" around the beads to incorporate the beads into the tire. At this stage, the partially assembled tire has a generally cylindrical, tubular shape.
At a desired stage of the tire building process, the shape of a partially manufactured tire is changed from its initial generally cylindrical, band-shaped configuration to a generally toroidal shape. Apparatus for assisting with this "shaping" of a partially built tire is well known to those who are skilled in the art, and many proposals have been made for improving such apparatus. For example, U.S. Pat. Nos. 4,683,021 and 4,226,656 issued Jul. 28, 1987 and Oct. 7, 1980, respectively, disclose the use of a variety of types of inflatable bladders to position and orient selected portions of tires during changes from generally cylindrical, band-like shapes to shapes that are generally toroidal.
A particularly problematic type of tire to shape without encountering problems of bead area distortion and malformation is a radial aircraft tire. Because aircraft tires typically must carry several hundred times their own weight, they tend to be stiffly reinforced and have bead portions that do not "slip" or "slide" easily within the confines of such "grooves" as may be provided at spaced locations about the periphery of a tire building drum to receive, retain and properly position the bead portions. No known prior proposal is believed to adequately meet the needs that are encountered in "rotating the beads" of radial aircraft tires.
A number of proposals have been made to address problem tendencies toward malformation and distortion that are encountered in bead areas of tires during bead rotation and shaping. One proposal seeks to employ a complex mechanical bead support assembly that has a large number of pivotally mounted bead support sectors that are intended to pivot in unison during bead rotation. Another proposal provides oil-enclosing membranes that line the surfaces of grooves of bead supports to provide what is referred to as an "oscillating unit" to facilitate surface sliding during bead rotation. No known prior proposal is believed to provide as simple, effective, long-lived and inexpensive a solution as does the present invention to the long-standing problem of bead area malformation and distortion during the shaping of newly formed green tire assemblies.